Commit 9f81654e authored by Andrii Nakryiko's avatar Andrii Nakryiko Committed by Alexei Starovoitov
Browse files

libbpf: Expose BTF-to-C type declaration emitting API 



Expose API that allows to emit type declaration and field/variable definition
(if optional field name is specified) in valid C syntax for any provided BTF
type. This is going to be used by bpftool when emitting data section layout as
a struct. As part of making this API useful in a stand-alone fashion, move
initialization of some of the internal btf_dump state to earlier phase.

Signed-off-by: default avatarAndrii Nakryiko <andriin@fb.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Acked-by: default avatarMartin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20191214014341.3442258-8-andriin@fb.com
parent 3d208f4c

tools/lib/bpf/btf.h

+22 −0
Original line number Diff line number Diff line
@@ -126,6 +126,28 @@ LIBBPF_API void btf_dump__free(struct btf_dump *d); 


LIBBPF_API int btf_dump__dump_type(struct btf_dump *d, __u32 id);



struct btf_dump_emit_type_decl_opts {

	/* size of this struct, for forward/backward compatiblity */

	size_t sz;

	/* optional field name for type declaration, e.g.:

	 * - struct my_struct <FNAME>

	 * - void (*<FNAME>)(int)

	 * - char (*<FNAME>)[123]

	 */

	const char *field_name;

	/* extra indentation level (in number of tabs) to emit for multi-line

	 * type declarations (e.g., anonymous struct); applies for lines

	 * starting from the second one (first line is assumed to have

	 * necessary indentation already

	 */

	int indent_level;

};

#define btf_dump_emit_type_decl_opts__last_field indent_level



LIBBPF_API int

btf_dump__emit_type_decl(struct btf_dump *d, __u32 id,

			 const struct btf_dump_emit_type_decl_opts *opts);



/*

 * A set of helpers for easier BTF types handling

 */

tools/lib/bpf/btf_dump.c

+42 −26
Original line number Diff line number Diff line
@@ -116,6 +116,8 @@ static void btf_dump_printf(const struct btf_dump *d, const char *fmt, ...) 
	va_end(args);

}



static int btf_dump_mark_referenced(struct btf_dump *d);



struct btf_dump *btf_dump__new(const struct btf *btf,

			       const struct btf_ext *btf_ext,

			       const struct btf_dump_opts *opts,
@@ -137,18 +139,39 @@ struct btf_dump *btf_dump__new(const struct btf *btf, 
	if (IS_ERR(d->type_names)) {

		err = PTR_ERR(d->type_names);

		d->type_names = NULL;

		btf_dump__free(d);

		return ERR_PTR(err);

	}

	d->ident_names = hashmap__new(str_hash_fn, str_equal_fn, NULL);

	if (IS_ERR(d->ident_names)) {

		err = PTR_ERR(d->ident_names);

		d->ident_names = NULL;

		btf_dump__free(d);

		return ERR_PTR(err);

		goto err;

	}

	d->type_states = calloc(1 + btf__get_nr_types(d->btf),

				sizeof(d->type_states[0]));

	if (!d->type_states) {

		err = -ENOMEM;

		goto err;

	}

	d->cached_names = calloc(1 + btf__get_nr_types(d->btf),

				 sizeof(d->cached_names[0]));

	if (!d->cached_names) {

		err = -ENOMEM;

		goto err;

	}



	/* VOID is special */

	d->type_states[0].order_state = ORDERED;

	d->type_states[0].emit_state = EMITTED;



	/* eagerly determine referenced types for anon enums */

	err = btf_dump_mark_referenced(d);

	if (err)

		goto err;



	return d;

err:

	btf_dump__free(d);

	return ERR_PTR(err);

}



void btf_dump__free(struct btf_dump *d)
@@ -175,7 +198,6 @@ void btf_dump__free(struct btf_dump *d) 
	free(d);

}



static int btf_dump_mark_referenced(struct btf_dump *d);

static int btf_dump_order_type(struct btf_dump *d, __u32 id, bool through_ptr);

static void btf_dump_emit_type(struct btf_dump *d, __u32 id, __u32 cont_id);
@@ -202,27 +224,6 @@ int btf_dump__dump_type(struct btf_dump *d, __u32 id) 
	if (id > btf__get_nr_types(d->btf))

		return -EINVAL;



	/* type states are lazily allocated, as they might not be needed */

	if (!d->type_states) {

		d->type_states = calloc(1 + btf__get_nr_types(d->btf),

					sizeof(d->type_states[0]));

		if (!d->type_states)

			return -ENOMEM;

		d->cached_names = calloc(1 + btf__get_nr_types(d->btf),

					 sizeof(d->cached_names[0]));

		if (!d->cached_names)

			return -ENOMEM;



		/* VOID is special */

		d->type_states[0].order_state = ORDERED;

		d->type_states[0].emit_state = EMITTED;



		/* eagerly determine referenced types for anon enums */

		err = btf_dump_mark_referenced(d);

		if (err)

			return err;

	}



	d->emit_queue_cnt = 0;

	err = btf_dump_order_type(d, id, false);

	if (err < 0)
@@ -1016,6 +1017,21 @@ static int btf_dump_push_decl_stack_id(struct btf_dump *d, __u32 id) 
 * of a stack frame. Some care is required to "pop" stack frames after

 * processing type declaration chain.

 */

int btf_dump__emit_type_decl(struct btf_dump *d, __u32 id,

			     const struct btf_dump_emit_type_decl_opts *opts)

{

	const char *fname;

	int lvl;



	if (!OPTS_VALID(opts, btf_dump_emit_type_decl_opts))

		return -EINVAL;



	fname = OPTS_GET(opts, field_name, NULL);

	lvl = OPTS_GET(opts, indent_level, 0);

	btf_dump_emit_type_decl(d, id, fname, lvl);

	return 0;

}



static void btf_dump_emit_type_decl(struct btf_dump *d, __u32 id,

				    const char *fname, int lvl)

{

tools/lib/bpf/libbpf.map

+1 −0
Original line number Diff line number Diff line
@@ -211,6 +211,7 @@ LIBBPF_0.0.6 { 


LIBBPF_0.0.7 {

	global:

		btf_dump__emit_type_decl;

		bpf_program__attach;

		btf__align_of;

} LIBBPF_0.0.6;

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